Looking for a Neutral Density Filter?

I'm looking for a Neutral Density Filter (and) for my Nikon D3100 (18-55mm & 55-200mm lenses). The diameter is ø 52mm on both lenses. I would like to have 2 and filters. One 4-Stop & one 6-Stop - I don't know how to see what stop the filters are. For example: does Hoya ND8 mean a 8-Stop and filter?

I was confused by this too!

ND2 - 1 stop - reduces light to half
ND4 - 2 stops - reduces light to quarter
ND8 - 3 stops - reduces light to one eighth
ND16 - 4 stops - reduces light to 1 sixteenth
ND32 - 5 stops - to 1/32nd
ND64 - 6 stops - to 1/64th

You can use them in combination so and ND2 and ND4 is same as ND8; 2 ND4's are same as ND16

You should try getting a fader and filter! I picked one up from ebay. It gives you the range of 2ND - 400ND.